Conventional magnetic devices such as, inductors and transformers, are typically constructed by winding turns of wire around a ferromagnetic core. An inductor 1 is shown in FIG. 1 and includes a magnetic core 2. A number of turns of wire are wrapped around the core 2 to form a winding 3. The inductance provided by inductor 1 is proportional to the number of turns included in the winding 3.
A transformer 4 is shown in FIG. 2 and includes primary winding 5 and secondary winding 6 wrapped around a core 7. The transformer 4 is employed to convert a voltage Vp to a voltage Vs. Voltage Vs, is equal to the voltage Vp multiplied by the ratio of the number of turns of wire around the core 7 (Ns) in the secondary winding 6 to the number of turns (Ns) in the primary winding 5. This relationship is expressed by the formula:
Vs=((Ns)/(Np)*Vp)
Conventional inductors and transformers, such as those shown in FIGS. 1 and 2, often suffer from a number of drawbacks. More particularly, the position of the winding turns with respect to the core in these devices influences various performance characteristics of the devices, such as leakage, and winding-to-winding capacitance. In cases where more than one transformer or inductor is being fabricated, imprecise device fabrication methods can cause variations in performance from device to device.
A significant amount of manual labor is required to fabricate these magnetic devices, especially in the winding of the wire around the cores in a controlled fashion. Therefore, it can be difficult to fabricate large quantities of these devices inexpensively while maintaining close manufacturing tolerances. In addition, significant design attention must be given to minimizing parasitic leakage inductance levels which waste power and reduce performance efficiency.
Conventional magnetic devices tend to be undesirably large in size owing to the large number of winding turns employed and the magnetic core construction. Many of these devices therefore, are unsuitable for use in applications where space is a concern as it is in the design of electrical power systems for satellites. For such applications, it is desirable to provide high performance transformers that are of compact size and weight.
It is an object of this invention to provide a unique structure for a high performance transformer which lends itself to a simplified manufacturing process. In addition it is an object of this invention to provide a method of manufacture which can maintain close tolerances in a reliable fashion. It is a further object of this invention to provide such performance benefits while reducing the overall weight and size of the device to enable its beneficial use in satellite systems.
A transformer is constructed having a core and windings assembled in a generally flat planar shape. The core is divided into first and second portions. The first and second core portions are constructed of a ferromagnetic material, such as ferrite, and each is comprised of a base and a plurality of integral projections extending generally perpendicular to the base. The core portions are further constructed to mate to form a continuous magnetic circuit. In the preferred embodiment each of the core portions are formed having an xe2x80x9cExe2x80x9d shaped cross section.
The winding assembly is constructed of stacked layers, each of the layers having conductive paths printed thereon. Each of the layers also has a centrally located opening which are aligned in the stacked position and the printed paths generally surround the opening.
The conductive paths of selected stacked layers are electrically interconnected to form a primary winding, and the conductive paths of the other stacked layers are electrically interconnected to form secondary windings. The winding assembly further includes insulating spacers disposed between adjacent winding layers to separate the adjacent conductive paths and prevent shorting and reduce leakage between individual winding paths.
The winding assembly is assembled over one of the core portions with the central projection of the core portion extending through the central opening of the stacked winding assembly. The assembly of the device is completed by mating the other core portion with the first portion to create a continuous magnetic circuit around and through the stacked windings.
In this manner a transformer or other magnetic device can be constructed to accommodate a wide variety of performance specifications. The manufacture of each of the elements can be controlled to close tolerances and can be adjusted to accommodate high power applications typically encountered in satellite systems while avoiding